[Dean2]

Screams vacuum leak, right? I can't find one!

My '03 SVT has been running crappy off and on for a few days and giving me both P1131 and P1132 codes. The brake pedal is pretty stiff. It seems to get better as it warms up, running moreso than brake feel. With the codes and hard brake pedal, I'm thinking vacuum leak that's somehow getting better when things heat up - something expanding to close a crack.

I've tried spraying brake cleaner at the intake from the MAF to the throttle body/intake manifold area, but am not finding anything. I've tried this both cold at high idle and after it's warmed up. Am I missing some vacuum line? Any other ideas?

I have not yet checked the plugs and compression, but will do so in the next hour or so.

Oh, and while I'm on the subject of intake... What's with the oval opening at the bottom of the air filter housing?

Thanks!

 

[Dean2]

Lesson of the day: Even if your fancy, computerized car tells you X, Y, or Z is wrong, start with the basics.

After checking the plugs, I noticed that the wire for #4 did not seat properly. I mashed it down as well as I could and cranked it up. It ran exceptionally badly and had a bunch of fuel in the exhaust. I swapped the wire out. Now the car's running just fine. I took it on a three or so mile drive and it ran like a champ. No codes came up. (They were popping up immediately after clearing them.)

I guess I must have convinced myself that the brake pedal felt differently when I thought I had a vacuum leak, unless someone has a good theory as to why the almost not connected spake plug would cause a difference there.

But, I'm still curious about the hole in the air filter housing!

 

[whynotthinkwhynot]

When the car isn't running good like that, you will have less vacuum, so you weren't imagining it. Remember you lose vacuum as you open the throttle, and when the car is running on 3 cyls you're opening the throttle more to get it moving. I don't think these cars have vacuum storage either- which might be something worth adding. Even if you had it, it's only a temp fix for moments of low vacuum, and wouldn't make a difference running on 3 cyls.

 

[Dean2]

That makes sense! Thanks for the explanation.